Chromosomes and Cellular Reproduction

17. Crossing over (genetic recombination) occurs in a .

Use the following information for questions 18-19

Pea plants have seven (7) different types of chromosomes.

18. The nucleus of a megaspore in a pea ovary would contain how many chromosomes?

*a. 7 b. 14 c. 21 d. 28 a. 7

19. A nucleus in the pea endosperm contains how many chromosomes?

*b. 21 c.14 d. 28

True/False

20. Errors in chromosome separation are rarely a problem for an organism. (F)

21. The prokaryotes include both the eubacteria and the archaea. (T)

22. Archaea are more closely related to eukaryotes than they are to eubacteria. (T)

23. Generally, chromosomes of eukaryotes are circular. (F)

24. Cells with a single set of chromosomes are called diploid. (F)

25. Daughter cells resulting from the completion of a cell cycle always have identical cytoplasmic content (F)

26. Histones are present in all types of organisms including eubacteria, archea, and eukaryotes. (F)

27. Progression through the different phases of the cell cycle is regulated by key transition points called checkpoints. (T)

Fill in the Blank

28. In a flowering plant, the male part of the flower (the stamen) produces haploid microsporocyte cells that divide by mitosis to produce sperm. A pollen grain that lands on a stigma grows a pollen tube to deliver 2 (how many?) sperm to the ovary. Fusion of a sperm with an egg produces a 2 n cell called a zygote To provide food for the developing embryo, a tissue called endosperm is produced through double fertilization. Endosperm has a ploidy of 3 n

29. In prokaryotes, replication usually begins at a specific place on the chromosome called the origin of replication

30. The nuclear matrix is the highly organized internal scaffolding of the nucleus.

31. The attachment point on the chromosome for spindle microtubules is the centromere

32. Cytokinesis refers to the splitting of the cytoplasm, separating one cell into two

33. Chromatin is a complex structure of DNA and proteins called histones.

34. Telomeres are located at the ends of the chromosomes and participate in limiting cell division.

Short-Answer Discussion

35. During prophase I of meiosis, crossing over is indicated by what microscopically visible structure?

Chiasmata (chiasma) or the synaptonemal complex

36. List two differences and two similarities between mitosis and meiosis.

Differences:

(1) Mitosis occurs in somatic (nonsex) cells; meiosis occurs in sex cells to produce gametes.

(2) Meiosis involves chromosome pairing (of homologous chromosomes); mitosis does not.

(3) Mitosis produces nonsex cells; meiosis produces gametes.

(4) Mitosis produces cells of the same ploidy; meiosis produces haploid cells from diploid cells.

(5) Meiosis has two consecutive divisions; mitosis has one.

(6) Mitosis produces two daughter cells; meiosis produces four daughter cells.

(7) Mitosis produces identical daughter cells; meiosis produces four different daughter cells.

Similarities:

(1) Both involve the separation of replicated chromosomes during cell division.